1. Field of the Invention
The invention relates to methods for sequestering and removing metals from solid, liquid or gaseous materials using thiolated bio-oils.
2. Description of the Prior Art
Most vegetable oils typically have a triacylglycerol structure with a glycerol backbone connected to three long-chain ester linkages. The hydrocarbon chains of the structure make the molecule hydrophobic and immiscible with water or lower alcohols. The ester groups and internal double bonds give ample routes for modification (Gunstone. Fatty Acid and Lipid Chemistry. Blackie Academic and Professional. Glasgow, UK. 1994. 252). A wide variety of such vegetable oil derivatives have been reported (Biermann et al. 2000. Angew. Chem. Int. Ed. 39:2206-2224; Biermann et al. 2011. Angew. Chem. Int. Ed. Engl. 50:3854-3871; Hwang et al. 2003. J. Am. Oil. Chem. Soc. 80:811-815; Sharma et al. 2008. Bioresource Technol. 99:7333-7340; Ionescu et al. 2011. J. Serbian Chem. Soc. 76:591-606; Biswas et al. 2008. J. Agric. Food Chem. 56:5611-5616; Biswas et al. 2007. Green Chem. 9:85-89; Biswas et al. 2009. J. Agric. Food Chem. 57:8136-8141), having a variety of applications. These derivatives have included sulfurized vegetable oils obtained by the reaction between elemental sulfur and vegetable oils to improve the antiwear properties of lubricants (Erikson et al. U.S. Pat. No. 4,134,845; Kammann and Phillips. 1985. J. Am. Oil Chem. Soc. 62:917-923; Rossrucker and Fessenbecker. Sulfur carriers. In: Lubricant Additives: Chemistry and Applications. Rudnick. Ed. CRC Press. Boca Raton, Fla. 2003. pp. 259-292; McDonald. Zinc dithiophosphates. In: Lubricant Additives: Chemistry and Applications. Rudnick. Ed. CRC Press. Boca Raton, Fla. 2003. pp. 29-44; Walling and Helmreich. 1959. J. Am. Chem. Soc. 81:1144-1148). The addition of H2S or alkanethiols to fatty acids or their esters has also been widely described (Kircher. 1964. J. Am. Oil Chem. Soc. 41:351-354; Schwab et al. 1968. J. Am. Oil Chem. Soc. 45:461-464; Gadd et al. 1996. Eur. patent 0713867; Schwab and Gast. 1970. J. Am. Oil Chem. Soc. 47:371-373). The synthesis of hydroxyl-thioether derivatives of vegetable oil from epoxidized oils as lubricants was described by Sharma et al. (2006. J. Agric. Food Chem. 54:9866-9872) and Erhan et al. (U.S. Pat. No. 7,279,448). More recently, Bantchev et al. described the production of sulfide-modified vegetable oil lubricants using butanethiol in UV-initiated thiol-ene reactions with vegetable oils (2009. J. Agric. Food Chem. 57:1282-1290).